Tag Archives: linux

Why Docker sounds like a revolution ?

20140418-082531.jpgThese two last days, I was participating to devoxx in Paris. One of the star topic of the event this year was Docker so I attempt different talk about this container technology I already has discovered in a previous JUG session. It was not an evidence that this technology was more than something interesting for DEV needing small, fast starting, small memory footprint, environment for testing. With my OPS hat, I did not catch the interest. This was before Devoxx and the different talk. The aspects I’ll detailed in this post have not been addressed during Devoxx, as much as I have seen, as mostly the DEV aspects have been addressed, I going to synthesize my opinion.

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Small ODROID-U3 platform coming out !

Really interesting tweet I just saw about the Odroid-U3 platform you can find following this link. This platform with the size of a Raspberry PI board is a 4 ARM core 1.7Gb (cortex A9) with 2GB included. Video is HDMI 1080p.Storage is MicroSD slot. The price is really low : 58$

You can ran even Android & Linux on it.

Compared to a RPI, this sound good for video/media box applications, better than RPI. For hacking this is largely different, as you can see on the picture, GPIO connector are not so easy to access. But, you can also purchase an extension shield providing all what you are expected with 36 GPIO. To build your own shield it could be more complicated than RPI. This let me go to a question I have since months … Why RPI is not becoming less and less expensive or more & more powerful ? it have now about 2 year old.

Less negative point : like any new board coming after Raspberry, the ecosystem is actually really smaller and all third party components (box, shields) is really limited.

Now, that said … I have to order one !

ODROID-U3
ODROID-U3
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Problem with nvidia raid and grub2

It’s not the first time I have some trouble to setup grub2 correctly with my nvidia raid system (also called fake-raid) … I did not find exactly why, but for sure i never try to install grub2 correctly from yast or in manual mode.

The first solution to find was : how to boot a fresh installed system when the bootloader has not been configured. The solution is here : http://www.supergrubdisk.org. This tool is really simple and so efficient to boot !  I recommend to have this in your linux emergency kit !

The second solution, once the system has start is to reinstall a bootloader. Here, in fact the solution is easy : destroy this f**** grub2 and replace it by the legacy really good grub ! lol

Then it works … last step to me: understand why gnome is taking so long to start ?!? or the answer is in the question …

I love Linux !

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Restoring a grub2 bootloader broken

After I had to change a hard drive for another my linux Opensuse 12.2 grub bootloader was broken, here are some of the learning of this debugging phase :

– Restore grub to the new disk

– Start kernel manually

– Fix hard drive references

At the end, the process to recreate the bootloader and particularly to recreate the initrd file was broken, and I assume bugged. To really make it works, I had to update the whole Linux and again at the end of the process the booloader based on grub2 was impossible to execute. The solution was to select Grub (version 1) and it worked. I assume it was possible before update the whole distribution to use yast2 booloader and choose grub instead of grub2.

When you get a message like waiting for device … to apear at boot, it may be because of the initrd does not contain the right modules to access the hard drive. It appears when the motherboard has been changed.

This article is mostly notes taken during this debugging phase … so do not consider it as an howto but as a list of command and possible way to debug this kind of issues…

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Activate Masquerading (NAT) on Linux router

To activate NAT on a Linux Box used as a router, just use the following line :

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

eth0 is the network interface able to access Internet directly

Then you can list the NAT entry in iptables with the following command

# iptables -t nat -L

You can get more details with:

# iptables -t nat -L -v

The conntrack tool also help to see what happen in the NAT

# conntrack -L --src-nat / --dst-nat

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